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Henze D, Majdi JA, Cohen ED. Effect of epiretinal electrical stimulation on the glial cells in a rabbit retinal eyecup model. Front Neurosci 2024; 18:1290829. [PMID: 38318467 PMCID: PMC10839094 DOI: 10.3389/fnins.2024.1290829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 01/03/2024] [Indexed: 02/07/2024] Open
Abstract
Introduction We examined how pulse train electrical stimulation of the inner surface of the rabbit retina effected the resident glial cells. We used a rabbit retinal eyecup preparation model, transparent stimulus electrodes, and optical coherence tomography (OCT). The endfeet of Müller glia processes line the inner limiting membrane (ILM). Methods To examine how epiretinal electrode stimulation affected the Müller glia, we labeled them post stimulation using antibodies against soluble glutamine synthetase (GS). After 5 min 50 Hz pulse train stimulation 30 μm from the surface, the retina was fixed, immunostained for Müller glia, and examined using confocal microscopic reconstruction. Stimulus pulse charge densities between 133-749 μC/cm2/ph were examined. Results High charge density stimulation (442-749 μC/cm2/ph) caused significant losses in the GS immunofluorescence of the Müller glia endfeet under the electrode. This loss of immunofluorescence was correlated with stimuli causing ILM detachment when measured using OCT. Müller cells show potassium conductances at rest that are blocked by barium ions. Using 30 msec 20 μA stimulus current pulses across the eyecup, the change in transretinal resistance was examined by adding barium to the Ringer. Barium caused little change in the transretinal resistance, suggesting under low charge density stimulus pulse conditions, the Müller cell radial conductance pathway for these stimulus currents was small. To examine how epiretinal electrode stimulation affected the microglia, we used lectin staining 0-4 h post stimulation. After stimulation at high charge densities 749 μC/cm2/ph, the microglia under the electrode appeared rounded, while the local microglia outside the electrode responded to the stimulated retina by process orientation inwards in a ring by 30 min post stimulation. Discussion Our study of glial cells in a rabbit eyecup model using transparent electrode imaging suggests that epiretinal electrical stimulation at high pulse charge densities, can injure the Müller and microglia cells lining the inner retinal surface in addition to ganglion cells.
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Affiliation(s)
- Dean Henze
- University of San Diego, San Diego, CA, United States
| | - Joseph A. Majdi
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
| | - Ethan D. Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, MD, United States
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2
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Bolon B. Toxicologic Pathology Forum Opinion: Rational Approaches to Expanded Neurohistopathology Evaluation for Nonclinical General Toxicity Studies and Juvenile Animal Studies. Toxicol Pathol 2023; 51:363-374. [PMID: 38288942 DOI: 10.1177/01926233231225239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Existing nervous system sampling and processing "best practices" for nonclinical general toxicity studies (GTS) were designed to assess test articles with unknown, no known, or well-known neurotoxic potential. Similar practices are applicable to juvenile animal studies (JAS). In GTS and JAS, the recommended baseline sampling for all species includes brain (7 sections), spinal cord (cervical and lumbar divisions [cross and longitudinal sections for each]), and 1 nerve (sciatic or tibial [cross and longitudinal sections]) in hematoxylin and eosin-stained sections. Extra sampling and processing (ie, an "expanded neurohistopathology evaluation" [ENHP]) are used for agents with anticipated neuroactivity (toxic ± therapeutic) of incompletely characterized location and degree. Expanded sampling incorporates additional brain (usually 8-15 sections total), spinal cord (thoracic ± sacral divisions), ganglia (somatic ± autonomic, often 2-8 total), and/or nerves (2-6 total) depending on the species and study objectives. Expanded processing typically adds special neurohistological procedures (usually 1-4 for selected samples) to characterize glial reactions, myelin integrity, and/or neuroaxonal damage. In my view, GTS and JAS designs should sample neural tissues at necropsy as if ENHP will be needed eventually, and when warranted ENHP may incorporate expanded sampling and/or expanded processing depending on the study objective(s).
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Rao DB, Hoberman AM, Brown PC, Varela A, Bolon B. Regulatory Perspectives on Juvenile Animal Toxicologic Pathology. Toxicol Pathol 2021; 49:1393-1404. [PMID: 34620014 DOI: 10.1177/01926233211046869] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The Society of Toxicologic Pathology's Annual Virtual Symposium (2021) included a session on "Regulatory Perspectives on Juvenile Animal Toxicologic Pathology." The following narrative summarizes the key concepts from the four talks included in this symposium session chaired by Drs Deepa Rao and Alan Hoberman. These encompass an overview of various global regulations impacting the conduct of juvenile animal studies in pharmaceutical drug development and chemical toxicity assessments in a talk by Dr Alan Hoberman. Given the numerous regulatory guidances and legal statutes that have covered the conduct of juvenile animal studies and the recent harmonization of these guidances for pharmaceuticals, Dr Paul Brown provided an update on the harmonization of these guidances for pharmaceuticals, in the recently finalized version of the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use S11 guidance document, "Nonclinical Safety Testing in Support of Development of Pediatric Medicines." The first two talks on regulations were followed by two talks focused on an evaluation of the postnatal development of two major organ systems relevant in juvenile animals. Dr Aurore Varela covered study design and endpoints impacting the skeletal system (bone), while Dr Brad Bolon presented a talk on the study design and conduct of neuropathology evaluations for the developing nervous system.
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Affiliation(s)
- Deepa B Rao
- Greenfield Pathology Services Inc., Greenfield, IN, USA
| | | | - Paul C Brown
- US Food and Drug Administration, Silver Spring, MD, USA
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Bolon B, Dostal LA, Garman RH. Neuropathology Evaluation in Juvenile Toxicity Studies in Rodents: Comparison of Developmental Neurotoxicity Studies for Chemicals With Juvenile Animal Studies for Pediatric Pharmaceuticals. Toxicol Pathol 2021; 49:1405-1415. [PMID: 34620000 DOI: 10.1177/01926233211045321] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The developmental neuropathology examination in juvenile toxicity studies depends on the nature of the product candidate, its intended use, and the exposure scenario (eg, dose, duration, and route). Expectations for sampling, processing, and evaluating neural tissues differ for developmental neurotoxicity studies (DNTS) for chemicals and juvenile animal studies (JAS) for pediatric pharmaceuticals. Juvenile toxicity studies typically include macroscopic observations, brain weights, and light microscopic evaluation of routine hematoxylin and eosin (H&E)-stained sections from major neural tissues (brain, spinal cord, and sciatic nerve) as neuropathology endpoints. The DNTS is a focused evaluation of the nervous system, so the study design incorporates perfusion fixation, plastic embedding of at least one nerve, quantitative analysis of selected brain regions, and sometimes special neurohistological stains. In contrast, the JAS examines multiple systems, so neural tissues undergo conventional tissue processing (eg, immersion fixation, paraffin embedding, H&E staining only). An "expanded neurohistopathology" (or "expanded neuropathology") approach may be performed for JAS if warranted, typically by light microscopic evaluation of more neural tissues (usually additional sections of brain, ganglia, and/or more nerves) or/and special neurohistological stains, to investigate specific questions (eg, a more detailed exploration of a potential neuroactive effect) or to fulfill regulatory requests.
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Yohannes AR, Jung CY, Shea KI, Wong WT, Beylin A, Cohen ED. The microglia response to electrical overstimulation of the retina imaged under a transparent stimulus electrode. J Neural Eng 2021; 18. [PMID: 33418555 DOI: 10.1088/1741-2552/abda0a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Accepted: 01/08/2021] [Indexed: 11/12/2022]
Abstract
OBJECTIVE We investigated using the morphological response of retinal microglia as indicators of tissue damage from electrical overstimulation by imaging them through an optically transparent stimulus electrode. APPROACH To track the microglia, we used a transgenic mouse where the microglia expressed a water soluble green fluorescent protein (GFP). The clear stimulus electrode was placed epiretinally on the inner limiting membrane and the microglia layers were imaged using time-lapse confocal microscopy. We examined how the microglia responded both temporally and spatially to local overstimulation of the retinal tissue. Using confocal microscope vertical image stacks, the microglia under the electrode were imaged at 2.5min intervals. The retina was overstimulated for a 5 minute period using 1msec 749μC/cm2/ph biphasic current pulses and changes in the microglia morphology were followed for 1 hour post stimulation. After the imaging period, a label for cellular damage was applied to the retina. MAIN RESULTS The microglia response to overstimulation depended on their spatial location relative to the electrode lumen and could result in 3 different morphological responses. Some microglia were severely injured and became a series of immotile ball-like fluorescent processes. Other microglia survived, and reacted rapidly to the injury by extending filopodia oriented toward the damage zone. This response was seen in inner retinal microglia outside the stimulus electrode edge. A third effect, seen with the deeper outer microglia under the electrode, was a fading of their fluorescent image which appeared to be due to optical scatter caused by overstimulation-induced retinal edema. SIGNIFICANCE The microglial morphological responses to electrical overstimulation injury occur rapidly and can show both direct and indirect effects of the stimulus electrode injury. The microglia injury pattern closely follows models of the electric field distribution under thinly insulated disc electrodes.
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Affiliation(s)
- Alula R Yohannes
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Bldg. 62 Rm 1204, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Christopher Yi Jung
- University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland, MD 21250, UNITED STATES
| | - Katherine I Shea
- CDER/Division of Applied Regulatory Science, US Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, MD 20993-0002, UNITED STATES
| | - Wai T Wong
- Section on Neuron-Glia Interactions in Retinal Disease, National Eye Institute, 6 Center Drive, Bethesda, Maryland, MD 20814, UNITED STATES
| | - Alexander Beylin
- Office of Product Quality and Evaluation, Center for Dev. and Rad. Health, FDA, Silver Spring, Maryland, UNITED STATES
| | - Ethan D Cohen
- Division of Biomedical Physics, Center for Dev. and Rad. Health, FDA, Office of Science and Engineering Labs, Bld 62 White Oak Fed Res Ctr., 10903 New Hampshire Ave, Silver Spring, Maryland, 20993, UNITED STATES
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6
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Bolon B, Krinke GJ, Pardo ID. Essential References for Structural Analysis of the Peripheral Nervous System for Pathologists and Toxicologists. Toxicol Pathol 2019; 48:87-95. [DOI: 10.1177/0192623319868160] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Toxicologic neuropathology for the peripheral nervous system (PNS) is a vital but often underappreciated element of basic translational research and safety assessment. Evaluation of the PNS may be complicated by unfamiliarity with normal nerve and ganglion biology, which differs to some degree among species; the presence of confounding artifacts related to suboptimal sampling and processing; and limited experience with differentiating such artifacts from genuine disease manifestations and incidental background changes. This compilation of key PNS neurobiology, neuropathology, and neurotoxicology references is designed to allow pathologists and toxicologists to readily access essential information that is needed to enhance their proficiency in evaluating and interpreting toxic changes in PNS tissues from many species.
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Howroyd PC. Dissection of the Trigeminal Ganglion of Nonrodent Species Used in Toxicology Studies. Toxicol Pathol 2019; 48:30-36. [PMID: 31181996 DOI: 10.1177/0192623319854338] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The ganglion of the trigeminal (V cranial) nerve is generally sampled at necropsy in nonrodent toxicology studies only when somatic or autonomic peripheral nervous system toxicity is suspected. The ganglion is far more difficult to locate in nonrodents than in rats and mice, and suitable methods to dissect it have been described only for swine. The trigeminal nerve caudal to the ganglion passes through a canal, roofed by bone in dogs and rabbits and by a tough layer of dura mater in swine and nonhuman primates. The ganglion is partly or wholly obscured by overlying dura mater. Of the 3 intracranial branches of the nerve, the ophthalmic is delicate and the maxillary and mandibular have extremely short courses within the cranial cavity. Methods that are practical in routine toxicologic pathology for the dissection of the ganglion in nonrodent laboratory species are illustrated and relevant species differences in the anatomy of the intracranial part of the trigeminal nerve are highlighted.
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Affiliation(s)
- Paul C Howroyd
- Charles River Laboratories Edinburgh, Tranent, United Kingdom
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8
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Juberg DR, Hoberman AM, Marty S, Picut CA, Stump DG. Letter to the editor regarding "safety of safety evaluation of pesticides: developmental neurotoxicity of chlorpyrifos and chlorpyrifos-methyl" by Mie et al. (environmental health. 2018. 17:77). Environ Health 2019; 18:21. [PMID: 30871546 PMCID: PMC6419458 DOI: 10.1186/s12940-019-0454-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Accepted: 02/14/2019] [Indexed: 05/21/2023]
Affiliation(s)
- Daland R. Juberg
- Human Health Science Policy, Corteva Agrisciences, Indianapolis, IN USA
| | - Alan M. Hoberman
- Global Developmental, Reproductive and Juvenile Toxicology, Charles River Laboratories, Horsham, PA USA
| | - Sue Marty
- Toxicology & Environmental Research and Consulting, The Dow Chemical Company, Midland, MI USA
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Fisher JE, Ravindran A, Elayan I. CDER Experience With Juvenile Animal Studies for CNS Drugs. Int J Toxicol 2019; 38:88-95. [DOI: 10.1177/1091581818824313] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A survey was undertaken to evaluate juvenile animal studies conducted for drug applications reviewed by the Center for Drug Evaluation and Research between 2009 and 2014. Some conclusions about the nonclinical pediatric safety assessment based on studies performed in support of central nervous system–active compounds are presented here. A total of 44 completed studies from 32 New Drug Applications submitted to the Divisions of Psychiatry and Neurology Products were evaluated. Data on animal species and age range used, endpoints evaluated, and outcomes included in labeling were analyzed. Of the drugs evaluated, all but one had studies conducted in rats. In some cases, a second study in a nonrodent species (dog) was also conducted. Indices of growth and development and standard general toxicity parameters were included in all of the studies. Expanded neurohistopathology evaluations, bone mineral density measurements, and reproductive and neurobehavioral functional assessments were also generally carried out. A variety of neurological and neurobehavioral tests were employed. In the majority of rat studies, the potential for long-term cognitive impairment was evaluated using a complex water maze. Juvenile animal studies provided safety information considered relevant to drug use in children and that was included in labeling for 78% of the applications surveyed. The most commonly reported findings in labeling were for neurobehavioral effects, including changes in locomotor activity, auditory startle habituation, and learning and memory. Of the studies described in labeling with neurobehavioral effects, 54% found these effects to be persistent and to provide evidence of developmental neurotoxicity.
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Affiliation(s)
- J. Edward Fisher
- Division of Neurology Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
| | - Arippa Ravindran
- Division of Psychiatry Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
| | - Ikram Elayan
- Division of Psychiatry Products, Center for Drug Evaluation and Research (CDER), Office of New Drugs (OND), US Food and Drug Administration (FDA), Silver Spring, MD, USA
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10
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Bolon B, Krinke G, Butt MT, Rao DB, Pardo ID, Jortner BS, Garman RH, Jensen K, Andrews-Jones L, Morrison JP, Sharma AK, Thibodeau MS. STP Position Paper: Recommended Best Practices for Sampling, Processing, and Analysis of the Peripheral Nervous System (Nerves and Somatic and Autonomic Ganglia) during Nonclinical Toxicity Studies. Toxicol Pathol 2018; 46:372-402. [DOI: 10.1177/0192623318772484] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Peripheral nervous system (PNS) toxicity is surveyed inconsistently in nonclinical general toxicity studies. These Society of Toxicologic Pathology “best practice” recommendations are designed to ensure consistent, efficient, and effective sampling, processing, and evaluation of PNS tissues for four different situations encountered during nonclinical general toxicity (screening) and dedicated neurotoxicity studies. For toxicity studies where neurotoxicity is unknown or not anticipated (situation 1), PNS evaluation may be limited to one sensorimotor spinal nerve. If somatic PNS neurotoxicity is suspected (situation 2), analysis minimally should include three spinal nerves, multiple dorsal root ganglia, and a trigeminal ganglion. If autonomic PNS neuropathy is suspected (situation 3), parasympathetic and sympathetic ganglia should be assessed. For dedicated neurotoxicity studies where a neurotoxic effect is expected (situation 4), PNS sampling follows the strategy for situations 2 and/or 3, as dictated by functional or other compound/target-specific data. For all situations, bilateral sampling with unilateral processing is acceptable. For situations 1–3, PNS is processed conventionally (immersion in buffered formalin, paraffin embedding, and hematoxylin and eosin staining). For situation 4 (and situations 2 and 3 if resources and timing permit), perfusion fixation with methanol-free fixative is recommended. Where PNS neurotoxicity is suspected or likely, at least one (situations 2 and 3) or two (situation 4) nerve cross sections should be postfixed with glutaraldehyde and osmium before hard plastic resin embedding; soft plastic embedding is not a suitable substitute for hard plastic. Special methods may be used if warranted to further characterize PNS findings. Initial PNS analysis should be informed, not masked (“blinded”). Institutions may adapt these recommendations to fit their specific programmatic requirements but may need to explain in project documentation the rationale for their chosen PNS sampling, processing, and evaluation strategy.
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Affiliation(s)
| | | | - Mark T. Butt
- Tox Path Specialists, LLC, Frederick, Maryland, USA
| | - Deepa B. Rao
- US Food and Drug Administration, Center for Drug Evaluation and Research, Silver Spring, Maryland, USA
| | | | - Bernard S. Jortner
- Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
| | - Robert H. Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | - Karl Jensen
- US Environmental Protection Agency, Research Triangle Park, North Carolina, USA
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Ramot Y, Schiffenbauer YS, Maronpot R, Nyska A. Compact Magnetic Resonance Imaging Systems-Novel Cost-Effective Tools for Preclinical Drug Safety and Efficacy Evaluation. Toxicol Sci 2018; 157:3-7. [PMID: 28329801 DOI: 10.1093/toxsci/kfx024] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Practical magnetic resonance imaging for use in investigative and preclinical toxicology studies is now feasible. Newly developed, self-containing imaging systems provide an efficient and cost-effective means to rapidly obtain in vivo and ex vivo magnetic resonance imaging images to improve how we perform toxicology and toxicologic pathology.
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Affiliation(s)
- Yuval Ramot
- Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | | | | | - Abraham Nyska
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel.,Toxicologic Pathology, Timrat, Israel
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12
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Bolon B. Regulatory Forum Opinion Piece*: Effective Brain Trimming for Regulatory-type Nonclinical Toxicity Studies. Toxicol Pathol 2017; 46:115-120. [DOI: 10.1177/0192623317749453] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Regulatory guidances for nonclinical toxicity testing require brain evaluation but do not require a specific analytical strategy. The Society of Toxicologic Pathology (STP) has produced “best practice” recommendations for brain sampling and processing in general toxicity (GT) studies in adult rodents and nonrodents as well as developmental neurotoxicity (DNT) studies in rodents. This article explains acceptable brain trimming strategies as described in these 2 STP documents. Figures in the DNT and GT “best practices” illustrate coronal brain trimming at specific levels as defined by discrete external and internal anatomic landmarks. However, the text of both “best practice” papers states that institutions may choose different brain trimming levels or other planes (e.g., a longitudinal orientation) as long as key structures are sampled and trimming is consistent among individuals across the study. The STP-recommended number of brain levels to evaluate (7 or 8 coronal sections for GT and DNT studies, respectively) may need to be increased if neurotoxicity is considered possible or likely based on in-life clinical findings or other risk factors (chemical structure, known mode of action, etc.).
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Chen VS, Morrison JP, Southwell MF, Foley JF, Bolon B, Elmore SA. Histology Atlas of the Developing Prenatal and Postnatal Mouse Central Nervous System, with Emphasis on Prenatal Days E7.5 to E18.5. Toxicol Pathol 2017; 45:705-744. [PMID: 28891434 DOI: 10.1177/0192623317728134] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Evaluation of the central nervous system (CNS) in the developing mouse presents unique challenges, given the complexity of ontogenesis, marked structural reorganization over very short distances in 3 dimensions each hour, and numerous developmental events susceptible to genetic and environmental influences. Developmental defects affecting the brain and spinal cord arise frequently both in utero and perinatally as spontaneous events, following teratogen exposure, and as sequelae to induced mutations and thus are a common factor in embryonic and perinatal lethality in many mouse models. Knowledge of normal organ and cellular architecture and differentiation throughout the mouse's life span is crucial to identify and characterize neurodevelopmental lesions. By providing a well-illustrated overview summarizing major events of normal in utero and perinatal mouse CNS development with examples of common developmental abnormalities, this annotated, color atlas can be used to identify normal structure and histology when phenotyping genetically engineered mice and will enhance efforts to describe and interpret brain and spinal cord malformations as causes of mouse embryonic and perinatal lethal phenotypes. The schematics and images in this atlas illustrate major developmental events during gestation from embryonic day (E)7.5 to E18.5 and after birth from postnatal day (P)1 to P21.
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Affiliation(s)
- Vivian S Chen
- 1 Charles River Laboratories Inc., Durham, North Carolina, USA.,Authors contributed equally
| | - James P Morrison
- 2 Charles River Laboratories Inc., Shrewsbury, Massachusetts, USA.,Authors contributed equally
| | - Myra F Southwell
- 3 Cellular Molecular Pathology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | - Julie F Foley
- 4 Bio-Molecular Screening Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
| | | | - Susan A Elmore
- 3 Cellular Molecular Pathology Branch, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
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14
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Li AA, Sheets LP, Raffaele K, Moser V, Hofstra A, Hoberman A, Makris SL, Garman R, Bolon B, Kaufmann W, Auer R, Lau E, Vidmar T, Bowers WJ. Recommendations for harmonization of data collection and analysis of developmental neurotoxicity endpoints in regulatory guideline studies: Proceedings of workshops presented at Society of Toxicology and joint Teratology Society and Neurobehavioral Teratology Society meetings. Neurotoxicol Teratol 2017; 63:24-45. [PMID: 28757310 PMCID: PMC6634984 DOI: 10.1016/j.ntt.2017.07.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Revised: 07/24/2017] [Accepted: 07/26/2017] [Indexed: 11/20/2022]
Abstract
The potential for developmental neurotoxicity (DNT) of environmental chemicals may be evaluated using specific test guidelines from the US Environmental Protection Agency or the Organisation for Economic Cooperation and Development (OECD). These guidelines generate neurobehavioral, neuropathological, and morphometric data that are evaluated by regulatory agencies globally. Data from these DNT guideline studies, or the more recent OECD extended one-generation reproductive toxicity guideline, play a pivotal role in children's health risk assessment in different world areas. Data from the same study may be interpreted differently by regulatory authorities in different countries resulting in inconsistent evaluations that may lead to inconsistencies in risk assessment decisions internationally, resulting in regional differences in public health protection or in commercial trade barriers. These issues of data interpretation and reporting are also relevant to juvenile and pre-postnatal studies conducted more routinely for pharmaceuticals and veterinary medicines. There is a need for development of recommendations geared toward the operational needs of the regulatory scientific reviewers who apply these studies in risk assessments, as well as the scientists who generate DNT data sets. The workshops summarized here draw upon the experience of the authors representing government, industry, contract research organizations, and academia to discuss the scientific issues that have emerged from diverse regulatory evaluations. Although various regulatory bodies have different risk management decisions and labeling requirements that are difficult to harmonize, the workshops provided an opportunity to work toward more harmonized scientific approaches for evaluating DNT data within the context of different regulatory frameworks. Five speakers and their coauthors with neurotoxicology, neuropathology, and regulatory toxicology expertise discussed issues of variability, data reporting and analysis, and expectations in DNT data that are encountered by regulatory authorities. In addition, principles for harmonized evaluation of data were suggested using guideline DNT data as case studies.
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Affiliation(s)
| | | | | | - Virginia Moser
- US EPA National Health and Environmental Effects Research Laboratory, Office of Research and Development (NHEERL, ORD), USA
| | | | - Alan Hoberman
- Charles River Laboratories, Global Developmental, Reproductive and Juvenile Toxicology, USA.
| | - Susan L Makris
- US EPA National Center for Environmental Assessment, Office of Research and Development (NCEA ORD), USA.
| | | | | | | | - Roland Auer
- University of Saskatchewan, Department of Pathology, Canada.
| | | | | | - Wayne J Bowers
- Department of Neuroscience, Carleton University, Ontario, Canada
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Dow GS, Brown T, Reid M, Smith B, Toovey S. Tafenoquine is not neurotoxic following supertherapeutic dosing in rats. Travel Med Infect Dis 2017; 17:28-34. [DOI: 10.1016/j.tmaid.2017.05.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Revised: 05/05/2017] [Accepted: 05/06/2017] [Indexed: 10/19/2022]
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16
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Schlemm L, Radbruch H, Brandt AU, Scheel M, Paul F. Histopathologic Assessment of Neurotoxicity after Repeated Administration of Gadodiamide in Healthy Rats. Radiology 2017; 282:925-926. [PMID: 28218886 DOI: 10.1148/radiol.2017162394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | - Friedemann Paul
- Departments of Neurology and
- Neuropathology
- Experimental and Clinical Research Center, Max Delbrueck Center for Molecular Medicine, Charité–Universitätsmedizin Berlin, Berlin, Germany
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Sharma AK, Morrison JP, Rao DB, Pardo ID, Garman RH, Bolon B. Toxicologic Pathology Analysis for Translational Neuroscience. Int J Toxicol 2016; 35:410-9. [DOI: 10.1177/1091581816636372] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A half-day American College of Toxicology continuing education course presented key issues often confronted by translational neuroscientists when predicting human risk from animal-derived toxicologic pathology data. Two talks correlated discrete structures with major functions in brains of rodents and nonrodents. The third lecture provided practical advice to obtain highly homologous rodent brain sections for quantitative morphometry in developmental neurotoxicity testing. The last presentation discussed demographic influences (eg, species, strain, sex, age), physiological attributes (eg, body composition, brain vascularity, pharmacokinetic/pharmacodynamic patterns, etc), and husbandry parameters (eg, group housing) recognized to impact the actions of neuroactive chemicals. Speakers described common cases of real-world challenges to animal data interpretation encountered when designing studies or extrapolating biological responses across species. The efficiency of translational neuroscience efforts will likely be enhanced as new methods (eg, high-resolution non-invasive imaging) improve our capability to cross-connect subtle anatomic and/or biochemical lesions with functional changes over time.
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Affiliation(s)
| | | | - Deepa B. Rao
- Center for Drug Evaluation and Research (CDER), US Food and Drug Administration, Silver Spring, MD, USA
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18
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Beekhuijzen M, Barentsen H, Marsden E, Zmarowski A, Aujoulat M, Picut C, Sloter E. Implementing the extended one-generation reproductive toxicity study (EOGRTS): important points to consider. Crit Rev Toxicol 2016; 46:332-47. [DOI: 10.3109/10408444.2015.1137863] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Sheets LP, Li AA, Minnema DJ, Collier RH, Creek MR, Peffer RC. A critical review of neonicotinoid insecticides for developmental neurotoxicity. Crit Rev Toxicol 2016; 46:153-90. [PMID: 26513508 PMCID: PMC4732412 DOI: 10.3109/10408444.2015.1090948] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/01/2015] [Accepted: 09/02/2015] [Indexed: 01/21/2023]
Abstract
A comprehensive review of published and previously unpublished studies was performed to evaluate the neonicotinoid insecticides for evidence of developmental neurotoxicity (DNT). These insecticides have favorable safety profiles, due to their preferential affinity for nicotinic receptor (nAChR) subtypes in insects, poor penetration of the mammalian blood-brain barrier, and low application rates. Nevertheless, examination of this issue is warranted, due to their insecticidal mode of action and potential exposure with agricultural and residential uses. This review identified in vitro, in vivo, and epidemiology studies in the literature and studies performed in rats in accordance with GLP standards and EPA guidelines with imidacloprid, acetamiprid, thiacloprid, clothianidin, thiamethoxam, and dinotefuran, which are all the neonicotinoids currently registered in major markets. For the guideline-based studies, treatment was administered via the diet or gavage to primiparous female rats at three dose levels, plus a vehicle control (≥20/dose level), from gestation day 0 or 6 to lactation day 21. F1 males and females were evaluated using measures of motor activity, acoustic startle response, cognition, brain morphometry, and neuropathology. The principal effects in F1 animals were associated with decreased body weight (delayed sexual maturation, decreased brain weight, and morphometric measurements) and acute toxicity (decreased activity during exposure) at high doses, without neuropathology or impaired cognition. No common effects were identified among the neonicotinoids that were consistent with DNT or the neurodevelopmental effects associated with nicotine. Findings at high doses were associated with evidence of systemic toxicity, which indicates that these insecticides do not selectively affect the developing nervous system.
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Affiliation(s)
| | - Abby A. Li
- Exponent Health Sciences,
San Francisco,
CA,
USA
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20
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Gill S, Hou Y, Li N, Pulido O, Bowers W. Developmental neurotoxicity of polybrominated diphenyl ethers mixture de71 in Sprague-Dawley rats. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2016; 79:482-93. [PMID: 27294297 DOI: 10.1080/15287394.2016.1182001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Polybrominated diphenyl ethers (PBDE) are a class of brominated flame retardants that are recognized as global environmental contaminants and a potential adverse health risk. The objective of this study was to evaluate the developmental impacts on rat Sprague-Dawley (SD) pups at postnatal day (PND) 11, 21, 50, 105, and 250 after perinatal exposure to a DE71 mixture. These PNDs corresponded to juveniles, young, and mature adults, respectively. The analysis included histopathological, transcriptional evaluation, and Western blots in both hippocampus and midbrain. There were no marked histopathological changes, but significant transcriptional alterations were observed at PND 21 and 250 in midbrain. These changes occurred in a number of the markers of the cholinergic system, including acetylcholinesterase, muscarinic and nicotinic receptors, and structural gene,s including those of neurofilaments, cell adhesion molecules including N-cadherin and CAMKII, and cytokines. The markers were upregulated at least twofold or greater at PND 21. These biomarkers were predominantly altered in males at low dose (0.3 mg/kg), whereas females were affected only at high concentration (30 mg/kg). At PND 250 both males and females showed downregulation of markers in both intermediate- and high-dose groups. Our results support the findings that in utero and lactational exposure to DE71 mixture leads to transcriptional alterations in midbrain of adult SD rats.
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Affiliation(s)
- Santokh Gill
- a Regulatory Toxicology Research Division , Health Products and Foods Branch, Health Canada , Ottawa , Ontario , Canada
| | - Yangxun Hou
- a Regulatory Toxicology Research Division , Health Products and Foods Branch, Health Canada , Ottawa , Ontario , Canada
| | - Nanqin Li
- b Hazard Identification Division , Environmental Health Science and Research Bureau, Health Canada , Ottawa , Ontario , Canada
| | - Olga Pulido
- c Departmental of Pathology and Laboratory Medicine , University of Ottawa , Ottawa , Ontario , Canada
| | - Wayne Bowers
- b Hazard Identification Division , Environmental Health Science and Research Bureau, Health Canada , Ottawa , Ontario , Canada
- d Department of Neuroscience , Carleton University , Ottawa , Ontario , Canada
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Taketa Y, Shiotani M, Tsuru Y, Kotani S, Osada Y, Fukushima T, Inomata A, Hosokawa S. Application of a compact magnetic resonance imaging system for toxicologic pathology: evaluation of lithium-pilocarpine-induced rat brain lesions. J Toxicol Pathol 2015; 28:217-24. [PMID: 26538811 PMCID: PMC4604131 DOI: 10.1293/tox.2015-0043] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Accepted: 08/07/2015] [Indexed: 11/29/2022] Open
Abstract
Magnetic resonance imaging (MRI) is a useful noninvasive tool used to detect lesions in clinical and veterinary medicine. The present study evaluated the suitability of a new easy-to-use compact MRI platform (M2 permanent magnet system, Aspect Imaging, Shoham, Israel) for assisting with preclinical toxicologic pathology examination of lesions in the rat brain. In order to induce brain lesions, male Sprague-Dawley rats were treated once with lithium chloride (127 mg/kg, intraperitoneal [i.p.]) followed by pilocarpine (30 mg/kg, i.p.). One week after dosing, the perfused, fixed brains were collected, analyzed by the MRI system and examined histopathologically. MRI of the brain of treated rats revealed areas of high T1 and middle to low T2 signals, when compared with the controls, in the piriform cortex, lateral thalamic nucleus, posterior paraventricular thalamic nucleus and posterior hypothalamic nucleus of the cerebrum. The altered MRI signal areas were consistent with well-circumscribed foci of neuronal cell degeneration/necrosis accompanied by glial cell proliferation. The present data demonstrated that quick analysis of fixed organs by the MRI system can detect the presence and location of toxicologic lesions and provide useful temporal information for selection of appropriate sections for histopathologic examination before routine slide preparation, especially in complex and functionally heterogeneous organs such as the brain.
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Affiliation(s)
- Yoshikazu Taketa
- Tsukuba Drug Safety, Global Drug Safety, Biopharmaceutical Assessments Core Function Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Motohiro Shiotani
- Tsukuba Drug Safety, Global Drug Safety, Biopharmaceutical Assessments Core Function Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Yoshiharu Tsuru
- Research Support Department, Primetech Corp., 1-3-25 Koishikawa, Bunkyo-ku, Tokyo 112-0002, Japan
| | - Sadaharu Kotani
- Neuroscience and General Medicine Product Creation Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Yoshihide Osada
- Neuroscience and General Medicine Product Creation Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Tatsuto Fukushima
- Neuroscience and General Medicine Product Creation Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Akira Inomata
- Tsukuba Drug Safety, Global Drug Safety, Biopharmaceutical Assessments Core Function Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
| | - Satoru Hosokawa
- Tsukuba Drug Safety, Global Drug Safety, Biopharmaceutical Assessments Core Function Unit, Eisai Product Creation Systems, Eisai Co., Ltd., 5-1-3 Tokodai, Tsukuba, Ibaraki 300-2635, Japan
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Garman RH, Li AA, Kaufmann W, Auer RN, Bolon B. Recommended Methods for Brain Processing and Quantitative Analysis in Rodent Developmental Neurotoxicity Studies. Toxicol Pathol 2015; 44:14-42. [PMID: 26296631 DOI: 10.1177/0192623315596858] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Neuropathology methods in rodent developmental neurotoxicity (DNT) studies have evolved with experience and changing regulatory guidance. This article emphasizes principles and methods to promote more standardized DNT neuropathology evaluation, particularly procurement of highly homologous brain sections and collection of the most reproducible morphometric measurements. To minimize bias, brains from all animals at all dose levels should be processed from brain weighing through paraffin embedding at one time using a counterbalanced design. Morphometric measurements should be anchored by distinct neuroanatomic landmarks that can be identified reliably on the faced block or in unstained sections and which address the region-specific circuitry of the measured area. Common test article-related qualitative changes in the developing brain include abnormal cell numbers (yielding altered regional size), displaced cells (ectopia and heterotopia), and/or aberrant differentiation (indicated by defective myelination or synaptogenesis), but rarely glial or inflammatory reactions. Inclusion of digital images in the DNT pathology raw data provides confidence that the quantitative analysis was done on anatomically matched (i.e., highly homologous) sections. Interpreting DNT neuropathology data and their presumptive correlation with neurobehavioral data requires an integrative weight-of-evidence approach including consideration of maternal toxicity, body weight, brain weight, and the pattern of findings across brain regions, doses, sexes, and ages.
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Affiliation(s)
- Robert H Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | - Abby A Li
- Exponent Inc., San Francisco, California, USA
| | | | - Roland N Auer
- Hôpital Ste-Justine, Département de Pathologie, Université de Montréal, Québec, Canada
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Majdi JA, Qian H, Li Y, Langsner RJ, Shea KI, Agrawal A, Hammer DX, Hanig JP, Cohen ED. The use of time-lapse optical coherence tomography to image the effects of microapplied toxins on the retina. Invest Ophthalmol Vis Sci 2014; 56:587-97. [PMID: 25525175 DOI: 10.1167/iovs.14-15594] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE We developed a novel technique for accelerated drug screening and retinotoxin characterization using time-lapse optical coherence tomography (OCT) and a drug microapplication device. METHODS Using an ex vivo rabbit eyecup preparation, we studied retinotoxin effects in real-time by microperfusing small retinal areas under a transparent fluoropolymer tube. Known retinotoxic agents were applied to the retina for 5-minute periods, while changes in retinal structure, thickness, and reflectance were monitored with OCT. The OCT images of two agents with dissimilar mechanisms, cyanide and kainic acid, were compared to their structural changes seen histologically. RESULTS We found the actions of retinotoxic agents tested could be classified broadly into two distinct types: (1) agents that induce neuronal depolarization, such as kainic acid, causing increases in OCT reflectivity or thickness of the inner plexiform and nuclear layers, and decreased reflectivity of the outer retina; and (2) agents that disrupt mitochondrial function, such as cyanide, causing outer retinal structural changes as evidenced by a reduction in the OCT reflectivity of the photoreceptor outer segment and pigment epithelium layers. CONCLUSIONS Retinotoxin-induced changes in retinal layer reflectivity and thickness under the microperfusion tube in OCT images closely matched the histological evidence of retinal injury. Time-lapse OCT imaging of the microperfused local retina has the potential to accelerate drug retinotoxicological screening and expand the use of OCT as an evaluation tool for preclinical animal testing.
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Affiliation(s)
- Joseph A Majdi
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Haohua Qian
- National Eye Institute, Visual Function Core, National Institutes of Health, Bethesda, Maryland, United States
| | - Yichao Li
- National Eye Institute, Visual Function Core, National Institutes of Health, Bethesda, Maryland, United States
| | - Robert J Langsner
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Katherine I Shea
- Office of Testing and Research, Center for Drug Evaluation and Research, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Anant Agrawal
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Daniel X Hammer
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Joseph P Hanig
- Office of Testing and Research, Center for Drug Evaluation and Research, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
| | - Ethan D Cohen
- Division of Biomedical Physics, Office of Science and Engineering Labs, Center for Devices and Radiological Health, Food and Drug Administration, White Oak Federal Research Labs, Silver Spring, Maryland, United States
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24
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Morrison JP, Sharma AK, Rao D, Pardo ID, Garman RH, Kaufmann W, Bolon B. Fundamentals of translational neuroscience in toxicologic pathology: optimizing the value of animal data for human risk assessment. Toxicol Pathol 2014; 43:132-9. [PMID: 25398755 DOI: 10.1177/0192623314558306] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A half-day Society of Toxicologic Pathology continuing education course on "Fundamentals of Translational Neuroscience in Toxicologic Pathology" presented some current major issues faced when extrapolating animal data regarding potential neurological consequences to assess potential human outcomes. Two talks reviewed functional-structural correlates in rodent and nonrodent mammalian brains needed to predict behavioral consequences of morphologic changes in discrete neural cell populations. The third lecture described practical steps for ensuring that specimens from rodent developmental neurotoxicity tests will be processed correctly to produce highly homologous sections. The fourth talk detailed demographic factors (e.g., species, strain, sex, and age); physiological traits (body composition, brain circulation, pharmacokinetic/pharmacodynamic patterns, etc.); and husbandry influences (e.g., group housing) known to alter the effects of neuroactive agents. The last presentation discussed the appearance, unknown functional effects, and potential relevance to humans of polyethylene glycol (PEG)-associated vacuoles within the choroid plexus epithelium of animals. Speakers provided real-world examples of challenges with data extrapolation among species or with study design considerations that may impact the interpretability of results. Translational neuroscience will be bolstered in the future as less invasive and/or more quantitative techniques are devised for linking overt functional deficits to subtle anatomic and chemical lesions.
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Affiliation(s)
| | | | - Deepa Rao
- National Toxicology Program, National Institute of Environmental Health Sciences and Integrated Laboratory Systems, Research Triangle Park, North Carolina, USA
| | | | - Robert H Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | | | - Brad Bolon
- The Ohio State University, College of Veterinary Medicine, Columbus, Ohio, USA
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25
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Defazio R, Criado A, Zantedeschi V, Scanziani E. Neuroanatomy-based Matrix-guided Trimming Protocol for the Rat Brain. Toxicol Pathol 2014; 43:249-56. [DOI: 10.1177/0192623314538345] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Brain trimming through defined neuroanatomical landmarks is recommended to obtain consistent sections in rat toxicity studies. In this article, we describe a matrix-guided trimming protocol that uses channels to reproduce coronal levels of anatomical landmarks. Both setup phase and validation study were performed on Han Wistar male rats (Crl:WI(Han)), 10-week-old, with bodyweight of 298 ± 29 ( SD) g, using a matrix (ASI-Instruments®, Houston, TX) fitted for brains of rats with 200 to 400 g bodyweight. In the setup phase, we identified eight channels, that is, 6, 8, 10, 12, 14, 16, 19, and 21, matching the recommended landmarks midway to the optic chiasm, frontal pole, optic chiasm, infundibulum, mamillary bodies, midbrain, middle cerebellum, and posterior cerebellum, respectively. In the validation study, we trimmed the immersion-fixed brains of 60 rats using the selected channels to determine how consistently the channels reproduced anatomical landmarks. Percentage of success (i.e., presence of expected targets for each level) ranged from 89 to 100%. Where 100% success was not achieved, it was noted that the shift in brain trimming was toward the caudal pole. In conclusion, we developed and validated a trimming protocol for the rat brain that allow comparable extensiveness, homology, and relevance of coronal sections as the landmark-guided trimming with the advantage of being quickly learned by technicians.
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Affiliation(s)
| | | | | | - Eugenio Scanziani
- Mouse and Animal Pathology Laboratory (MAPLab), Filarete Foundation, Milan, Italy
- Department of Veterinary Sciences and Public Health, University of Milan, Milan, Italy
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26
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Yoshizawa K, Emoto Y, Kinoshita Y, Yuri T, Tsubura A. N-methyl-N-nitrosourea-induced cerebellar hypoplasia in rats: Effect of arachidonic acid supplementation during the gestational, lactational and post-weaning periods. Exp Ther Med 2013; 6:627-634. [PMID: 24137238 PMCID: PMC3786806 DOI: 10.3892/etm.2013.1219] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/02/2013] [Indexed: 01/08/2023] Open
Abstract
Arachidonic acid (AA) is a fatty acid that is important for visual and brain development and is commonly added as a functional food ingredient to commercial infant formulas worldwide. However, few studies have examined whether AA supplementation during neonatal life has an effect on neuronal abnormalities. In the present study, the effect of dietary AA supplementation in dams during gestation and lactation was investigated by examining N-methyl-N-nitrosourea (MNU)-induced cerebellar hypoplasia in young Lewis rats. Dams were fed a 2.0% AA diet or a basal diet (<0.01% AA). At birth (postnatal day 0), male and female pups received a single intraperitoneal injection of 35 mg/kg MNU or vehicle. Brain weights were measured and a morphological analysis of macroscopic and histological specimens was conducted after 7, 14, 21, 28 and 60 days. Irrespective of whether the rats had been fed an AA diet, the brain weights of the MNU-treated rats, particularly the weights of the cerebellum, were decreased compared with those of the MNU-untreated rats from the 14th day following the MNU injection. Macroscopic reductions in the cerebellar length and/or width and histologically observed reductions in cerebellar vertex height and/or cortex width were also detected in the MNU-treated rats, irrespective of whether the rats had been fed with AA. Histopathologically, the MNU-treated rats (irrespective of AA supplementation) exhibited disorganization of the cerebellar cortex and disarrangement of the cortical layers (loss and/or disturbance of the molecular, Purkinje and granular cell layers). There were no significant differences in any parameters among the MNU-treated rats, irrespective of whether the rats had been fed an AA diet. In conclusion, an AA-rich diet for dams during gestation and lactation did not modify MNU-induced cerebellar hypoplasia in their offspring.
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Affiliation(s)
- Katsuhiko Yoshizawa
- Department of Pathology II, Kansai Medical University, Hirakata, Osaka 573-1010, Japan
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27
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Bolon B, Garman RH, Pardo ID, Jensen K, Sills RC, Roulois A, Radovsky A, Bradley A, Andrews-Jones L, Butt M, Gumprecht L. STP position paper: Recommended practices for sampling and processing the nervous system (brain, spinal cord, nerve, and eye) during nonclinical general toxicity studies. Toxicol Pathol 2013; 41:1028-48. [PMID: 23475559 DOI: 10.1177/0192623312474865] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The Society of Toxicologic Pathology charged a Nervous System Sampling Working Group with devising recommended practices to routinely screen the central nervous system (CNS) and peripheral nervous system (PNS) in Good Laboratory Practice-type nonclinical general toxicity studies. Brains should be weighed and trimmed similarly for all animals in a study. Certain structures should be sampled regularly: caudate/putamen, cerebellum, cerebral cortex, choroid plexus, eye (with optic nerve), hippocampus, hypothalamus, medulla oblongata, midbrain, nerve, olfactory bulb (rodents only), pons, spinal cord, and thalamus. Brain regions may be sampled bilaterally in rodents using 6 to 7 coronal sections, and unilaterally in nonrodents with 6 to 7 coronal hemisections. Spinal cord and nerves should be examined in transverse and longitudinal (or oblique) orientations. Most Working Group members considered immersion fixation in formalin (for CNS or PNS) or a solution containing acetic acid (for eye), paraffin embedding, and initial evaluation limited to hematoxylin and eosin (H&E)-stained sections to be acceptable for routine microscopic evaluation during general toxicity studies; other neurohistological methods may be undertaken if needed to better characterize H&E findings. Initial microscopic analyses should be qualitative and done with foreknowledge of treatments and doses (i.e., "unblinded"). The pathology report should clearly communicate structures that were assessed and methodological details. Since neuropathologic assessment is only one aspect of general toxicity studies, institutions should retain flexibility in customizing their sampling, processing, analytical, and reporting procedures as long as major neural targets are evaluated systematically.
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Affiliation(s)
- Brad Bolon
- 1The Ohio State University, Columbus, Ohio, USA
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28
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Kaufmann W, Bolon B, Bradley A, Butt M, Czasch S, Garman RH, George C, Gröters S, Krinke G, Little P, McKay J, Narama I, Rao D, Shibutani M, Sills R. Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems. Toxicol Pathol 2012; 40:87S-157S. [PMID: 22637737 DOI: 10.1177/0192623312439125] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).
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Tsuji R, Crofton KM. Developmental neurotoxicity guideline study: issues with methodology, evaluation and regulation. Congenit Anom (Kyoto) 2012; 52:122-8. [PMID: 22925212 DOI: 10.1111/j.1741-4520.2012.00374.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Recently social concerns have been increasing about the effects of environmental factors on children's health, especially on their nervous systems. The U.S. Environmental Protection Agency (EPA) and the Organisation for Economic Co-operation and Development (OECD) have published testing guidelines for developmental neurotoxicity (DNT). Approximately 110 guideline studies have been conducted to date. Importantly, information from these studies has provided data critical for regulatory decisions for a number of chemicals. However, the DNT guidelines do not always satisfy all stakeholders because of some uncertainties in their methodology, evaluation, and regulation. Methodological issues include incomplete harmonization between EPA and OECD guidelines, criticisms of the methodology for learning and memory testing, and unspecified positive control substances. Potential artifacts in morphometric neuropathological measures, criteria for observation measures, uncertainty of postnatal offspring exposure, especially in feeding studies, and extrapolation of data from rats to humans are major evaluation issues. In addition, there is some uncertainty in the use of an additional safety factor for susceptibility of infants and children. Moreover, the DNT guidelines have extensive time and cost requirements, use large numbers of animals, and there is a limited set of laboratories that can conduct the study. This paper reviews some of these issues and summarizes discussions from the symposium 'Developmental neurotoxicity testing: Scientific approaches towards the next generation to protecting the developing nervous system of children' held at the 2011 annual meeting of the Japanese Teratology Society.
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Affiliation(s)
- Ryozo Tsuji
- Environmental Health Science Laboratory, Sumitomo Chemical Co. Ltd, Osaka, Japan.
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Cohen E, Agrawal A, Connors M, Hansen B, Charkhkar H, Pfefer J. Optical coherence tomography imaging of retinal damage in real time under a stimulus electrode. J Neural Eng 2011; 8:056017. [DOI: 10.1088/1741-2560/8/5/056017] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Bolon B, Couto S, Fiette L, Perle KL. Internet and Print Resources to Facilitate Pathology Analysis When Phenotyping Genetically Engineered Rodents. Vet Pathol 2011; 49:224-35. [DOI: 10.1177/0300985811415709] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Genetically engineered mice and rats are increasingly used as models for exploring disease progression and mechanisms. The full spectrum of anatomic, biochemical, and functional changes that develop in novel, genetically engineered mouse and rat lines must be cataloged before predictions regarding the significance of the mutation may be extrapolated to diseases in other vertebrate species, including humans. A growing list of reference materials, including books, journal articles, and websites, has been produced in the last 2 decades to assist researchers in phenotyping newly engineered rodent lines. This compilation provides an extensive register of materials related to the pathology component of rodent phenotypic analysis. In this article, the authors annotate the resources they use most often, to allow for quick determination of their relevance to research projects.
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Affiliation(s)
- B. Bolon
- The Ohio State University, Columbus, Ohio
| | - S. Couto
- Genentech, Inc., South San Francisco, California
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32
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Bolon B. Perspectives on past practices and future trends in toxicologic neuropathology: notes from a keynote address by Dr. Peter S. Spencer. Toxicol Pathol 2010; 39:15-8. [PMID: 21075919 DOI: 10.1177/0192623310385147] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Dr. Peter S. Spencer, a pioneering neurotoxicologist of international renown, delivered the keynote address at the 2010 Joint Scientific Symposium of the Society of Toxicologic Pathology (STP) and the International Federation of Societies of Toxicologic Pathologists (IFSTP). He has made many landmark discoveries during his four-decade career. Dr. Spencer's address communicated several fundamental principles of past and present toxicologic neuropathology research, and he also predicted future trends in the field. First, classic approaches to toxicologic neuropathology emphasized morphologic techniques such as light microscopic and ultrastructural assessment. However, neuropathology methods alone rarely reveal the mechanism(s) and etiology of neurotoxic conditions, so neurotoxicity problems are now being investigated using a multidisciplinary approach in which neuropathologic assessment is but one component of the analysis. The two primary trends for future toxicologic neuropathology investigations, in both animals and humans, will be an increased use of noninvasive neural imaging and greater preference for in situ molecular ("omic") methods, which provide functional information in a structural context. These trends will significantly enhance the ability of scientists to translate animal data to human situations, thereby improving our understanding of disease mechanisms and facilitating efforts to design new therapies for neural diseases.
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33
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Bolon B, Bradley A, Garman RH, Krinke GJ. Useful Toxicologic Neuropathology References for Pathologists and Toxicologists. Toxicol Pathol 2010; 39:234-9. [DOI: 10.1177/0192623310385142] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Investigations in toxicologic neuropathology are complex undertakings because of the intricate spatial and temporal diversity in the anatomic, functional, and molecular organization of the central and peripheral nervous systems. This compilation of toxicologic neuropathology resources has been designed to consolidate a broad range of useful neurobiology, neuropathology, and neurotoxicology resources in a single reference. This collection will increase familiarity with the basic knowledge, skills, and tools required for the proficient practice of toxicologic neuropathology and should help to improve the analysis and interpretation of pathology data sets from neural tissues in toxicology studies.
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Affiliation(s)
| | - Alys Bradley
- Charles River Laboratories, Preclinical Services, Edinburgh EH33 2NE, Scotland, United Kingdom
| | - Robert H. Garman
- Consultants in Veterinary Pathology, Inc., Murrysville, Pennsylvania, USA
| | - Georg J. Krinke
- Pathology Evaluations (PATHEV), 4402 Frenkendorf, Switzerland
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Bolon B, Garman RH, Gundersen HJG, Allan Johnson G, Kaufmann W, Krinke G, Little PB, Makris SL, Mellon RD, Sulik KK, Jensen K. Continuing education course #3: current practices and future trends in neuropathology assessment for developmental neurotoxicity testing. Toxicol Pathol 2010; 39:289-93. [PMID: 21075916 DOI: 10.1177/0192623310386247] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The continuing education course on Developmental Neurotoxicity Testing (DNT) was designed to communicate current practices for DNT neuropathology, describe promising innovations in quantitative analysis and noninvasive imaging, and facilitate a discussion among experienced neuropathologists and regulatory scientists regarding suitable DNT practices. Conventional DNT neuropathology endpoints are qualitative histopathology and morphometric endpoints of particularly vulnerable sites (e.g., cerebral, cerebellar, or hippocampal thickness). Novel imaging and stereology measurements hold promise for automated analysis of factors that cannot be effectively examined in routinely processed specimens (e.g., cell numbers, fiber tract integrity). The panel recommended that dedicated DNT neuropathology data sets be acquired on a minimum of 8 sections (for qualitative assessment) or 3 sections (for quantitative linear and stereological analyses) using a small battery of stains to examine neurons and myelin. Where guidelines permit discretion, immersion fixation is acceptable for younger animals (postnatal day 22 or earlier), and peripheral nerves may be embedded in paraffin. Frequent concerns regarding DNT data sets include false-negative outcomes due to processing difficulties (e.g., lack of concordance among sections from different animals) and insensitive analytical endpoints (e.g., qualitative evaluation) as well as false-positive results arising from overinterpretation or misreading by inexperienced pathologists.
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Boyce JT, Boyce RW, Gundersen HJ. Choice of morphometric methods and consequences in the regulatory environment. Toxicol Pathol 2010; 38:1128-33. [PMID: 20884817 DOI: 10.1177/0192623310385141] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In certain cases, quantitative tissue structural data derived from tissue sections may be required to make critical decisions in the drug development or risk assessment process. Most frequently, these questions center on test article-related effects on cell number. In this opinion article, the limitations of estimating cell number by standard cell or nuclear profile counts from sections/blocks collected for routine histopathology are discussed from both a scientific and regulatory perspective and contrasted with the robust, sensitive, statistically based methods of design-based stereology. Specific existing industry practices are reviewed. Recent advances in stereological theory, software, hardware, and automated immunohistochemical staining now make it feasible to implement unbiased stereological methods to assess test article-related effects on cell number in a regulatory toxicology setting. These design-based stereological methods for counting cells are recommended when the quantification of small changes in cell number is critical to the risk assessment or decision-making process. These methods provide levels of sensitivity and statistical guarantees of accuracy that no other currently available tissue section-based methodology can provide.
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Affiliation(s)
- John T Boyce
- WIL Research Laboratories LLC, Ashland, Ohio 44805, USA.
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Raffaele KC, Rowland J, May B, Makris SL, Schumacher K, Scarano LJ. The use of developmental neurotoxicity data in pesticide risk assessments. Neurotoxicol Teratol 2010; 32:563-72. [PMID: 20398750 DOI: 10.1016/j.ntt.2010.04.053] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Revised: 01/29/2010] [Accepted: 02/03/2010] [Indexed: 10/19/2022]
Abstract
Following the passage of the Food Quality Protection Act, which mandated an increased focus on evaluating the potential toxicity of pesticides to children, the number of guideline developmental neurotoxicity (DNT) studies (OPPTS 870.6300) submitted to the U.S. Environmental Protection Agency (EPA) Office of Pesticide Programs (OPP) was greatly increased. To evaluate the impact of available DNT studies on individual chemical risk assessments, the ways in which data from these studies are being used in pesticide risk assessment were investigated. In addition, the neurobehavioral and neuropathological parameters affected at the lowest observed adverse effect level (LOAEL) for each study were evaluated to ascertain whether some types of endpoints were consistently more sensitive than others. As of December 2008, final OPP reviews of DNT studies for 72 pesticide chemicals were available; elimination of studies with major deficiencies resulted in a total of 69 that were included in this analysis. Of those studies, 15 had been used to determine the point of departure for one or more risk assessment scenarios, and an additional 13 were determined to have the potential for use as a point of departure for future risk assessments (selection is dependent upon review of the entire database available at the time of reassessment). Analysis of parameters affected at the study LOAELs indicated that no single parameter was consistently more sensitive than another. Early assessment time points (e.g., postnatal day (PND) 11/21) tended to be more sensitive than later time points (e.g., PND 60). These results demonstrate that data generated using the current guideline DNT study protocol are useful in providing points of departure for risk assessments. The results of these studies also affirm the importance of evaluating a spectrum of behavioral and neuropathological endpoints, in both young and adult animals, to improve the detection of the potential for a chemical to cause developmental neurotoxicity.
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Affiliation(s)
- Kathleen C Raffaele
- Office of Research and Development, U.S. Environmental Protection Agency, 1200 Pennsylvania Ave., Washington, DC 20460, USA.
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Bolon B, Anthony DC, Butt M, Dorman D, Green MV, Little PB, Valentine WM, Weinstock D, Yan J, Sills RC. “Current Pathology Techniques” Symposium Review: Advances and Issues in Neuropathology. Toxicol Pathol 2008. [DOI: 10.1177/0192623308322313] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Our understanding of the mechanisms that incite neurological diseases has progressed rapidly in recent years, mainly owing to the advent of new research instruments and our increasingly facile ability to assemble large, complex data sets acquired across several disciplines into an integrated representation of neural function at the molecular, cellular, and systemic levels. This mini-review has been designed to communicate the principal technical advances and current issues of importance in neuropathology research today in the context of our traditional neuropathology practices. Specific topics briefly addressed in this paper include correlative biology of the many facets of the nervous system; conventional and novel methods for investigating neural structure and function; theoretical and technical issues associated with investigating neuropathology end points in emerging areas of concern (developmental neurotoxicity, neurodegenerative conditions); and challenges and opportunities that will face pathologists in this field in the foreseeable future. We have organized this information in a manner that we hope will be of interest not only to professionals with a career focus in neuropathology, but also to general pathologists who occasionally face neuropathology questions.
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Affiliation(s)
| | - Douglas C. Anthony
- University of Missouri, Department of Pathology and Anatomical Sciences, Columbia, Missouri, USA
| | - Mark Butt
- Tox Path Specialists, Walkersville, Maryland, USA
| | - David Dorman
- North Carolina State University, College of Veterinary Medicine, Raleigh, North Carolina, USA
| | | | - Peter B. Little
- Charles River Laboratories, Research Triangle Park, North Carolina, USA
| | | | | | - James Yan
- Hospira Inc., Lake Forest, Illinois, USA
| | - Robert C. Sills
- National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, USA
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Chu I, Bowers WJ, Caldwell D, Nakai J, Wade MG, Yagminas A, Li N, Moir D, El Abbas L, Håkansson H, Gill S, Mueller R, Pulido O. Toxicological effects of in utero and lactational exposure of rats to a mixture of environmental contaminants detected in Canadian Arctic human populations. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH. PART A 2008; 71:93-108. [PMID: 18080900 DOI: 10.1080/15287390701612811] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
As part of the program to investigate mixture effects of environmental pollutants, this study describes clinical, biochemical, and histopathological effects in rats perinatally exposed to a mixture of persistent organochlorine pollutants and methylmercury that simulates the blood contaminant profile of humans residing in the Canadian Arctic. Groups of pregnant rats were administered orally 0, 0.05, 0.5, or 5 mg/kg body weight (bw)/d of a reconstituted mixture of organochlorine pollutants (referred to as mixture hereafter) from gestational day (GD) 1 to postnatal day (PND) 23. Positive and vehicle controls were given Aroclor 1254 (Aroclor hereafter, 15 mg/kg bw) and corn oil (vehicle), respectively. After parturition, the pups were colled to 8 per litter on PND 4, and killed on PND 35, 77, or 350, when tissues were collected for analysis. Gestational and lactational exposure of rats to mixture up to 5 mg/kg bw produced adverse effects in the offspring, including growth suppression, decreased spleen and thymic weights, increased serum cholesterol and liver microsomal enzyme activities, lower liver retinoid levels, and histological changes in the liver, thyroid, and spleen. Histological changes in the liver consisted of hepatic inflammation, vacuolation, and hypertrophy, while alterations in the thyroid were characterized by hypertrophy and hyperplasia of follicles. The hepatic and thyroidal effects were mild even at the highest dose. The spleen showed a dose-dependent atrophy in the lymphoid nodules and periarteriolar lymphatic sheath regions. Aroclor produced effects similar to those seen in the highest mixture group. In summary, this study demonstrates that exposure to the reconstituted mixture at 5 mg/kg bw produced growth suppression, changes in organ weights, and biochemical and histopathological changes in liver, thyroid, and spleen. This study also demonstrated that the blood level in rats given the 5-mg/kg dose, where most of the effects were observed, is 100-fold higher than the blood level in the 0.05-mg/kg group, which is comparable to that found in humans living in the Canadian Arctic region.
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Affiliation(s)
- Ih Chu
- Environmental and Occupational Toxicology Division, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, Ontario, Canada.
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Crofton KM, Foss JA, Hass U, Jensen KF, Levin ED, Parker SP. Undertaking positive control studies as part of developmental neurotoxicity testing: a report from the ILSI Research Foundation/Risk Science Institute expert working group on neurodevelopmental endpoints. Neurotoxicol Teratol 2007; 30:266-87. [PMID: 17681747 DOI: 10.1016/j.ntt.2007.06.002] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2007] [Revised: 04/26/2007] [Accepted: 06/07/2007] [Indexed: 10/23/2022]
Abstract
Developmental neurotoxicity testing involves functional and neurohistological assessments in offspring during and following maternal and/or neonatal exposure. Data from positive control studies are an integral component in developmental neurotoxicity risk assessments. Positive control data are crucial for evaluating a laboratory's capability to detect chemical-induced changes in measured endpoints. Positive control data are also valuable in a weight-of-evidence approach to help determine the biological significance of results and provide confidence in negative results from developmental neurotoxicity (DNT) studies. This review is a practical guide for the selection and use of positive control agents in developmental neurotoxicology. The advantages and disadvantages of various positive control agents are discussed for the endpoints in developmental neurotoxicity studies. Design issues specific to positive control studies in developmental neurotoxicity are considered and recommendations on how to interpret and report positive control data are made. Positive control studies should be conducted as an integral component of the incorporation and use of developmental neurotoxicity testing methods in laboratories that generate data used in risk decisions.
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Affiliation(s)
- Kevin M Crofton
- Neurotoxicology Division, NHEERL, ORD, US EPA, Research Triangle Park, NC, USA.
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Kaufmann W, Gröters S. Developmental neuropathology in DNT-studies—A sensitive tool for the detection and characterization of developmental neurotoxicants. Reprod Toxicol 2006; 22:196-213. [PMID: 16781841 DOI: 10.1016/j.reprotox.2006.04.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2006] [Revised: 04/10/2006] [Accepted: 04/10/2006] [Indexed: 11/18/2022]
Abstract
Developmental neurotoxicity (DNT-) studies are the first reproduction toxicity studies for which an extended histopathological examination of developing structures is required by the current EPA and OECD guidelines. The morphological screening includes a macroscopic evaluation of the brain and nervous tissue, brain weight parameters, gross morphometry of the brain, neurohistological examinations and a quantitative analysis of major brain areas. This review is intended to give an overview about the needs according to guideline requirements, practical approaches for a successful developmental neuropathology and its preconditions and does include examples of background data on the value and functional meaning of morphological data. A selection of experimental data from literature is also presented in the light of their contribution for the understanding of important, neurodevelopmental disorders in humans.
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Affiliation(s)
- Wolfgang Kaufmann
- Department of Product Safety, Regulations, Experimental Toxicology and Ecology, BASF AG, Ludwigshafen, Germany.
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